In the course of the past thirty years, the motor vehicle industry has benefited from technological progress in the field of electronics. Systems that used to be purely mechanical are now made up using knowledge in various fields of mechanics, hydraulics, and electronics, these various systems being known, for example, as “mechatronics systems.” These “mechatronics systems” make it possible to increase very markedly the performances of the vehicle for an advanced command.
Among these “mechatronics systems,” wheel anti lock brake systems or ABS systems can be mentioned, which prevent wheels from blocking during braking phases of the vehicle. By avoiding this blocking, the tires can then generate a higher braking force and thus optimize the braking distance of the vehicle.
Steering systems of vehicles have also been improved. Historically, hydraulic assistance has first made it possible to reduce the amount of force that the driver must provide to the steering wheel. Presently, the electric power steering named “EPS system” tends to replace this hydraulic power steering technology.
Futures innovations will concern in particular systems that make it possible to add torque to the power column (Torque Overlay), thus making it possible to assist the driver in certain situations by orienting the steering wheel, steer-by-wire control systems in which there is no longer a mechanical link between the steering wheel and the wheels, and where only electrical data is transported by an electrical bus, etc. In the area of these new technologies, systems of the “EFS”, activation of electrical or hydraulic steering, or “steer-by-wire” type offer a new degree of freedom which is a new parameter in the adjustment of the ground connection functions of the vehicle.
This degree of freedom makes it possible to add torque to the steering column, which makes it possible, either to vary the driving torque, or to effect auto-rotation of the steering wheel, which was impossible with only a hydraulic power steering system. This new function makes it possible, then, to improve the performances of the vehicle in many life situations, such as, in particular, compensation of lateral pull, “split-mu” braking assistance, etc., but also during maneuvering of the vehicle at low speed, where it is then possible to help the driver so that he needs to provide less work to the steering wheel to carry out the maneuvers.
The main function of a motor vehicle power steering system is to turn the steered wheels, for example, the front wheels of the vehicle, in order to steer the vehicle. This is usually carried out from a steering wheel, a steering column, a pinion, a rack, and tie rods. In order to reduce the effort in the area of the steering wheel, power steering systems have been introduced. These used to be hydraulic systems because of the power needed. However, nowadays, small high-power electric motors are starting to appear. Power steering is thus shifting to electric systems called “EPS systems.” The wheels are still mechanically linked to the steering wheel and any rotation of the steering wheel causes the steered wheels of the vehicle to turn.